Here are a few simple box framing type of judging things that help to judge quick if a buck is actually big, then pick apart. I can do this pretty quickly and then I get into the rack bracketing that Mike uses to really break the bucks down.
Big deer look big, look for the big buck head bob, the giants almost look cartoonish when they walk.
If the fronts are as tall as the backs, pay attention! Generally speaking, that is a mature deer with good fronts, look at all the bucks in this thread for reference.
Frame is everything, fronts as tall as the backs and wider than the ears generally is a buck to pay attention to.
An easy way to judge mass is measure the bases against the base of the ears. Then measure it all relative to that.
Mass hides inches and from there it is just a matter of adding up the points and main beam length.